scholarly journals A consideration of the correct calculation of thermodynamic parameters of adsorption

2007 ◽  
Vol 72 (12) ◽  
pp. 1363-1367 ◽  
Author(s):  
Slobodan Milonjic
Keyword(s):  
Free Energy ◽  
Thermodynamic Parameters ◽  
Freundlich Isotherm ◽  
Free Energy Of Adsorption ◽  
Correct Calculation ◽  
Adsorption Processes ◽  
Isotherm Equations ◽  
Henry Constants

The Langmuir and Freundlich isotherm equations have been widely used for interpreting various adsorption processes. There are, however, many serious mistakes in the literature in determination or calculation of thermodynamic parameters, especially in the determination of the change in the free energy of adsorption using Langmuir, Freundlich and Henry constants. Many authors used these constants for the determination of ?G expressed instead of dimensionless in some concentration units (for example: l mol-1, l g-1, ml mg-1, etc.).

scholarly journals Determination of the surface properties of kaolinite by inverse gas chromatography

2018 ◽  
Vol 2017 (2) ◽  
pp. 319-328 ◽  
Author(s):  
Ceyda Bilgiç
Keyword(s):  
Gas Chromatography ◽  
Free Energy ◽  
Inverse Gas Chromatography ◽  
Specific Enthalpy ◽  
Free Energy Of Adsorption ◽  
Dispersive Component ◽  
Enthalpy Of Adsorption ◽  
Kaolinite Surface ◽  
Acceptor Numbers

Abstract Inverse gas chromatography (IGC) was applied to characterize the surface of kaolinite. The adsorption thermodynamic parameters (the standard enthalpy (∆H0), entropy (∆S0) and free energy of adsorption (∆G0), the dispersive component of the surface energy (γsd), and the acid/base character of kaolinite surface were estimated by using the retention time of different non-polar and polar probes at infinite dilution region. The specific free energy of adsorption (∆Gsp), the specific enthalpy of adsorption (∆Hsp), and the specific entropy of adsorption (∆Ssp) of polar probes on kaolinite were determined. (∆Gsp) values were correlated with the donor and modified acceptor numbers of the probes to quantify the acidic (KA) and the basic (KD) parameters of the kaolinite surface. The values obtained for the parameters KA and KD indicated a basic character for kaolinite surface.

scholarly journals AVALIAÇÃO DOS PARÂMETROS TERMODINÂMICOS E CINÉTICOS DE CENOURAS SUBMETIDAS A SECAGEM CONVECTIVA

e-xacta ◽  
2017 ◽  
Vol 10 (2) ◽  
pp. 73 ◽  
Author(s):  
Heloísa Righi Pessoa da Silva ◽  
Roberta Pazinato Cuco ◽  
Barbara Daniele Almeida Porciuncula ◽  
Camila Da Silva
Keyword(s):  
Experimental Data ◽  
Free Energy ◽  
Mathematical Models ◽  
Thermodynamic Parameters ◽  
Kinetic Data ◽  
Temperature Characteristic ◽  
Different Temperatures ◽  
Endothermic Process ◽  
Degree Of Order

<p>Este estudo tem como objetivo a obtenção de dados cinéticos da secagem de cenouras, bem como o ajuste de modelos matemáticos aos dados experimentais e determinação dos parâmetros termodinâmicos do processo. Buscando este propósito, experimentos foram conduzidos em estufa com renovação e circulação de ar, nas temperaturas de 50, 60, 70 e 80 °C. Os modelos matemáticos foram ajustados aos dados das cinéticas de secagem à diferentes temperaturas, e os modelos de Page e de Midilli apresentaram o maior coeficiente de correlação (R<sup>2</sup>) e menor valor de RMSE. Da análise termodinâmica verificou-se que a entalpia e a energia livre de Gibbs diminuíram com o aumento da temperatura, característico de um processo endotérmico. A entropia apresentou valores negativos e diminuiu com a diminuição na temperatura de secagem, isto indica que há um aumento no grau de ordem do sistema, considerado desfavorável entropicamente.</p><p> </p><p>ABSTRACT</p><p>This study aims to obtain kinetic data of carrot drying, as well as the adjustment of mathematical models to the experimental data and determination of the thermodynamic parameters of the process. For this purpose, experiments were conducted in an oven with renovation and circulation of air, at temperatures of 50, 60, 70 and 80 °C. The mathematical models were adjusted to the drying kinetics data at different temperatures, and the Page and de Midilli models presented the highest correlation coefficient (R<sup>2</sup>) and lowest RMSE values. From the thermodynamic analysis it was verified that the enthalpy and the free energy of Gibbs decreased with the increase of the temperature, characteristic of an endothermic process. The entropy presented negative values and decreased with the decrease in the drying temperature, this indicates that there is an increase in the degree of order of the system, considered as entropically unfavorable.</p>

scholarly journals Determination of the optimal conditions for the adsorption of cadmium ions and phenol on chestnut(Castanea sativa) shell

2013 ◽  
Vol 11 (2) ◽  
pp. 196-204 ◽  
Keyword(s):  
Statistical Analysis ◽  
Adsorption Equilibrium ◽  
Castanea Sativa ◽  
Freundlich Isotherm ◽  
Individual Factors ◽  
Phenol Removal ◽  
Optimal Conditions ◽  
Cadmium Ions ◽  
Adsorption Processes

Adsorption of cadmium ions and phenol from aqueous solutions on chestnut (Castanea sativa) shell was studied. An incomplete 33 factorial design was applied to investigate the influence of the initial cadmium ions (20-60-100 mg l-1) or phenol concentration (0.01-0.255- 0.5 g l-1), temperature (10-25-40ºC for cadmium and 10-35-60ºC for phenol) and pH (5.5-7.0- 8.5 for Cd2+ ions and 2.5-6.0-9.5 for phenol) on the amount of contaminant adsorbed and on the adsorption percentage. Statistical analysis of the results showed the significance of the individual factors and their interactions on both adsorption processes. The best conditions for high cadmium ions and phenol removal within the experimental ranges of the variables studied were the natural pH (around 5.5) and a temperature of 25ºC for cadmium ions and 60ºC for phenol. Under these conditions, adsorption equilibrium was modelled by the Freundlich isotherm for cadmium ions and by the Langmuir isotherm for phenol.

Large Amplitude Thermal Fluctuations of Confined Semiflexible Biopolymer Filaments

2014 ◽  
Vol 81 (11) ◽  
Author(s):  
F. Jonsdottir ◽  
L. B. Freund
Keyword(s):  
Free Energy ◽  
Partition Function ◽  
Thermodynamic Parameters ◽  
Large Amplitude ◽  
Small Amplitude ◽  
Thermal Fluctuations ◽  
Single Filament ◽  
Amplitude Fluctuations ◽  
Active Interest

The phenomenon of thermal fluctuations of biopolymers has been of active interest for some time with a view toward understanding the effect of filament confinement, migration, and bonding. In this study, we focus our attention on planar fluctuations of a single filament between parallel confining surfaces. Filament slopes, with respect to the centerline of the channel, commonly exceed 0.1 in magnitude and therefore fall outside the range of small amplitude fluctuations. Consequently, large amplitudes are anticipated from the outset. Determination of the partition function leads to the quantitative dependence of free energy and other thermodynamic parameters on the degree of confinement.

Preparation and Investigation on the Adsorption Behavior of Polyethylene Glycol Modified Sodium Alginate Porous Membrane Adsorbent for Cr(III) Ions

2012 ◽  
Vol 455-456 ◽  
pp. 786-795
Author(s):  
Jian Hua Chen
Keyword(s):  
Polyethylene Glycol ◽  
Sodium Alginate ◽  
Low Cost ◽  
Freundlich Isotherm ◽  
Porous Membrane ◽  
Order Kinetic ◽  
Kinetic Experiment ◽  
Isotherm Equation ◽  
Adsorption Processes ◽  
Isotherm Equations

- In this study, sodium alginate based porous membrane adsorbents (GA/SA) were prepared by using polyethylene glycol (PEG) as porogen and glutaraldehyde (GA) as cross-linking agent. The prepared GA/SA were used to remove Cr (III) ions from wastewater to test its adsorption performance. The proposed technique is very convenient for operation. The batch experiments were performed to investigate the adsorption kinetics of Cr (III) ions from aqueous solution under different conditions, such as the amount of PEG in the GA/SA, pH of solution, initial Cr (III) ions concentration, adsorbent dose and contact time. The GA/SA exhibited the maximum uptake capacity of 57.4 mg/g under the optimal condition. The experiment results show that the adsorption is high pH-dependent. Various kinetic models were applied to examine the mechanism of adsorption processes. Pseudo-second-order kinetic model exhibits the best correlation with experimental data. The kinetic experiment results show that the adsorption of Cr (III) ions is a multistep limited adsorption process. Out of Langmuir and Freundlich isotherm equations, the batch equilibrium data are better described by the Freundlich isotherm equation. The prepared GA/SA could be considered as a potential low-cost and high-effective bio-sorbent for removing and recovering Cr (III) ions from the aqueous solutions.

Determination of the Free Energy of Adsorption on Carbon Blacks of a Nonionic Surfactant from Aqueous Solutions

Langmuir ◽  
2000 ◽  
Vol 16 (8) ◽  
pp. 3950-3956 ◽  
Author(s):  
C. M. González-García ◽  
M. L. González-Martín ◽  
V. Gómez-Serrano ◽  
J. M. Bruque ◽  
L. Labajos-Broncano
Keyword(s):  
Free Energy ◽  
Aqueous Solutions ◽  
Nonionic Surfactant ◽  
Free Energy Of Adsorption ◽  
Carbon Blacks

Models of Thermodynamic Properties of Prominences

1979 ◽  
Vol 44 ◽  
pp. 349-355
Author(s):  
R.W. Milkey
Keyword(s):  
Thermodynamic Properties ◽  
Mass Transport ◽  
Emission Spectrum ◽  
Thermodynamic Parameters ◽  
Working Group ◽  
Physical Processes ◽  
Theoretical Concepts ◽  
Group 3 ◽  
Observational Techniques

The focus of discussion in Working Group 3 was on the Thermodynamic Properties as determined spectroscopically, including the observational techniques and the theoretical modeling of physical processes responsible for the emission spectrum. Recent advances in observational techniques and theoretical concepts make this discussion particularly timely. It is wise to remember that the determination of thermodynamic parameters is not an end in itself and that these are interesting chiefly for what they can tell us about the energetics and mass transport in prominences.

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